Conventional rotary blades used for grass and weed trimming present the serious risks of rocks, pebbles, sticks and other debris being thrown by the rotating blades. The risk of thrown debris is presented not only to the operator of the rotary trimmer but also to bystanders and even pets in the immediate vicinity. Attempts to solve the problem include the use of shields or shrouds around the rotating blade in order to deflect the flying debris. Use of the shields and shrouds do not fully protect against the hazards associated with the flying debris since a segment of the shield around the rotating blade must be left open to allow for convenient cutting.
Conventional metal cutting blades present the additional risk of severe cutting injuries to the user and others by virtue of the rapidly rotating exposed blades. When in motion the blades can engage a hard unyielding object such as a tree trunk or fence post causing the trimmer to kick out or thrust out of control of the operator. The thrusting spinning blade then presents a serious cutting hazard. Shields and shrouds used to protect against direct blade contact with unyielding objects and eliminate thrusting do not afford complete protection because an area must remain open to allow the blade to cut. Further, the shields or shrouds often interfere with and impede the cutting performance of the trimmer and can restrict the use of the trimmer by making it more difficult for the trimmer to fit into tight places or more difficult to turn the trimmer for use as an edger.
String trimmers designed to protect the user and others from cutting injuries do not solve the problem of thrown debris. Flying debris is still a significant problem when string trimmers are used in place of a rotating blade and shielding and shrouding is often necessary. Further, string trimmers do not have the capacity, strength and durability in most instances to cut heavy grass and small shrubbery. When the speed and diameter of the rotating string is increased to enhance the cutting capabilities of string trimmers there seems to be a corresponding increase in the incidence of thrown rocks and debris.
Attempts at providing non-metal cutting blades, such as those illustrated in U.S. Pat. No. 4,250,622 to E. R. Houle, to reduce the injury risks associated with rotating metal blades have been made. However, non-metal blades do not provide the necessary strength and durability for heavy use and conventional designs do not eliminate the hazard of thrown debris.
Thus, there has been a long need for a functional rotary trimmer blade with the cutting and durability inherent in a metal blade that eliminates or minimizes the hazards of debris being thrown by the rotating blades common to conventional rotary trimmer blades and string trimmers and at the same time reduce the risk of cutting injuries to the user and others in the vicinity often associated with blade thrusting.